So is have a Problem that i did not find online. Its a Thermal runaway but not while cooling. Its while the Printer is getting heated up to start the print. The Setting ist 230°C and it just goes past it until its to far away at around 255 to 260 and then the thermal runaway error appears. The weird thing is i put a multimeter between and the Voltage drops off from 24v to 10V or so when it gets close to the temperature that it should reach. But it signals that the temperature is increasing and it is increasing because you can hear the filament "burning". I changed the heating part on the hotend. i dond have a temp sesor in reserve to check that. Is the Board maybe damaged? i would not know why but i am out of ideas. Maybe someone of you knows this problem.
RE: Thermal Runaway
Both Hotends messured at 18 Ohm at 28°C
The Thermistor of the Hotend messured 84kOhm at 28°C